Resumen:

This paper studies how the presence of an antitrust authority affects market-sharing
agreements made by firms in oligopolistic markets. These agreements prevent firms from
entering each other´s market. The set of market-sharing agreements defines a collusiveThis paper studies how the presence of an antitrust authority affects market-sharing
agreements made by firms in oligopolistic markets. These agreements prevent firms from
entering each other´s market. The set of market-sharing agreements defines a collusive
network, which is under suspicion by antitrust authorities. This paper shows that, from the firm´s
point of view, the probability of being caught is endogenous and depends on the agreements
each firm has signed. Stable collusive networks can be decomposed into a set of isolated firms
and complete alliances of different sizes. While in the absence of the antitrust authority, a
network is stable if its alliances are large enough, when the antitrust authority is considered, the
network is stability depends on the network configuration as a whole. Antitrust laws may have a
pro-competitive effect as they give Firms in large alliances more incentives to cut their
agreements at once.[+][-]